The instant invention relates to flow measuring devices and more particularly to a differential-pressure-type flow measuring device which is adapted for measuring the flow rates of fluids carrying entrained solids therein.
A wide variety of differential-pressure-type flow measuring devices have been heretofore-available for use in various different flow measurement applications. In this connection, most of the heretofore-available differential-pressure-type flow measuring devices have generally comprised flow tubes having sequentially disposed inlet, converging and throat sections, and they have had pressure sensing taps in the inlet and throat sections thereof for sensing the pressures therein. Flow measuring devices of this general type have been operative for providing indications of the flow rates of fluids passing through the flow tubes thereof by applying the differential pressures which are sensed between the inlet and throat sections thereof in well-known flow equations which are calibrated for specific applications. In any event, differential-pressure-type flow measuring devices of this general type have been constructed in various diferent dimensions and proportions in order to adapt them for meeting the needs of various specific applications. Specific exmples of devices of this type are found in the applicant's U.S. Pat. Nos. 4,516,434 and 4,528,847.
It has been found that while differential-pressure-type flow measuring devices of the above-described type can be effectively used for measuring the flow rates of most fluids, they often cannot be effectively utilized for measuring the flow rates of fluids having significant quantities of entrained solids therein. This is because most of the heretofore-available differential-pressure-type flow measuring devices have been constructed with open pressure sensing taps for sensing the pressures in the inlet and throat sections thereof, and when they have been used for measuring the flow rates of fluids carrying entrained solids therein, the open pressure sensing taps thereof have tended to become rapidly clogged by the solids. In order to overcome this problem, differential-pressure-type flow measuring devices having closed diaphragm-type pressure sensors have been developed for measuring the flow rates of fluids having entrained solids therein. However, while it has been found that flow measuring devices of this type are substantially less susceptible to becoming clogged than conventional differential-pressure-type flow measuring devices, even the heretofore-available devices having diaphragm-type pressure sensors have had significant disadvantages. Specifically, it has been found that when a diaphragm-type flow measuring device malfunctions, it is generally necessary to remove it from service, because it is generally not possible to repair, replace, or unclog the diaphragm-type sensors of a device of this type while the devices is in service. It is also generally necessary to recalibrate a device of this type at an off-site location after it has been repaired.
The instant invention provides an effective flow measuring device which overcomes many of the problems and disadvantages of the heretofore-available devices for measuring the flow rates of fluids bearing entrained solids. Specifically, the flow measuring device of the instant invention comprises a flow tube having sequentially disposd inlet, converging, and throat sections, wherein the inlet and throat sections each have substantially uniform diameters, and first and second pressure sensing means which communicate with the inlet and throat sections, respectively, for sensing the pressures therein. However, at least one of the pressure sensing means of the device comprises a tubular housing portion which is mounted in the flow tube so that it extends outwardly therefrom and so that the interior of the housing portion communicates with the interior of the flow tube, and a pressure sensing diaphragm element which is received in the housing portion so that it communicates with the interior of the flow tube for sensing the pressure in the adjacent section thereof. The housing portion and the diphragm element of the device are constructed so that the diaphragm element is slidable in sealed relation in the housing portion between a first position wherein it is disposed adjacent the flow tube and a second position wherein it is spaced outwardly therefrom, and the device further comprises means which is receivable in the housing portion when the diaphragm element is in the second position thereof for providing a sealed obstruction between the diaphragm element and the interior of the flow tube. Preferably, the first and second pressure sensing means each comprise a tubular housing portion, a diaphragm element, and means for providing a sealed obstruction in the housing portion thereof, and preferably the sealed obstruction means of each of the housing portions comprises a gate valve having a gate which is receivable between the adjacent diaphragm element and the interior of the flow tube when the adjacent diaphragm element is in the second position thereof. Further, preferably each of the housing portions has a manometer tap formed therein which is positioned so that when the adjacent diaphragm element is in the second position thereof and the obstruction means of the housing portion is in a withdrawn nonobstructing position, the manometer tap communicates with the adjacent section of the interior of the flow tube through the housing portion. Accordingly, when a manometer is connected to the manometer tap, it can be utilized for providing an indication of the true pressure in the adjacent section of the flow tube in order to properly calibrate the adjacent diaphragm element. Preferably, the diaphragm elements of the flow measuring device are of cylindrical configuration, and the housing portions preferably have O-rings therein which allow the diaphragm elements to be slidably repositioned in sealed relation in their respective housing portions. Further, the diaphragm elements are preferably dimensioned so that they have diameters which are less than approximately one-fourth of the diameter of the throat section of the flow tube.
During use and operation of the device of the instant invention under normal operating conditions, the diaphragm elements provide effective indications of the pressures in the inlet and throat sections of the flow tube, and these pressures can be applied in a flow equation to provide an indication of the flow rate of a fluid passing through the flow tube. In the event that one of the diaphragm elements malfunctions, it can be moved outwardly in its respective housing portion, the adjacent gate valve on the housing portion can be closed, and the diaphragm element can then be checked or replaced. Further, when the same or a new diaphragm element is inserted in the housing portion and positioned therein so that it is in its outwardly disposed position, the adjacent manometer tap can be connected to a manometer and the gate valve on the housing portion opened in order to calibrate the diaphragm element without allowing fluid to leak out of the device. In this connection, since the manometer tap in the housing portion is normally only used for short periods of time, it is not likely to become clogged; although even if it should become clogged, it can easily be unclogged by closing the adjacent gate valve and inserting a probe into the manometer tap. As a result, the device of the instant invention can be effectively calibrated without removing it from a flow system, and in most cases the flow system does not need to be shut down to repair the device.
Accordingly, it is a primary object of the instant invention to provide an effective device in measuring the flow rate of a fluid bearing entrained solids.
Another object of the instant invention is to provide an effective device for measuring the flow rate of a fluid bearing entrained solids which can be calibrated without removing it from a flow system.
A still further object of the instant invention is to provide a device for measuring the flow rate of a fluid bearing entrained solids wherein the device comprises a diaphragm element which is removable while a fluid is passing through the device.